Study on On-line Detecting of Transformer Winding Deformation Based on Parameter Identification of Leakage Inductance

Transformers are required to demonstrate the ability to withstand short circuit currents.In practice,overcurrents caused by short circuit can give rise to windings deformation,which is a main form of hidden health trouble or fault of transformer.Thus,on-line detecting of transformer winding deformation is of practical significance for the safe and reliable operation of the transformer.In this paper,a novel method is proposed to monitor the state of transformer windings,which is achieved through on-line detecting the leakage inductance of the windings.This method is based on the fact that the windings deformation can cause the variation of the leakage inductance of the transformer.First,the equivalent circuit equation of the transformer is given to derive the model for identifying the leakage inductance of the windings.Then,this equation is utilized to identify the leakage inductance of the windings by using the least square algorithm(LSA).Furthermore,the effect of magnetizing current,measurement errors and model inaccuracy on the identification error are analyzed,and the corrected model is also given to decrease this adverse effect on the results.Finally,the dynamic test is carried out to verify the method.From the test results,some conclusions can be drawn as follows.(1) The identification results are accurate.The omission of magnetizing current may affect the leakage inductance identified on-line,which can be weakened by compensation.(2) The identification algorithm is stable.The identification results will not influenced by the fluctuation of load or power factor.(3) Compared with the results from off-line measurement,the method can correctly identify the leakage inductance when the simulated deformation of windings develops.The test results clearly show that the method is very accurate even under the fluctuation of load or power factor.Therefore,the method can be effectively used to on-line detect the windings deformation.